This invention relates to a brake warning device.
The present invention has particular utility in the heavy truck and trailer industry as it has application to the dual air brake systems of truck/tractor and trailer units, with the intention of providing a warning of possible air brake system failure or malfunction. It is particularly, but not exclusively, intended to provide a warning of potential failure arising out of incorrect operation of the in-cab brake valves, which can potentially result in no service brake pressure to the trailer, therefore, leading to the potential for a serious crash situation. The warning device, however, can also provide warning of no, or lowered, service brake pressure arising out of other failure defective or defect situations.
A situation which can occur, even with an experienced operator, and the tractor/trailer braking system complying with land transport safety standards, and being well maintained, arises out of incorrect operation of the in-cab valves for actuating and releasing the tractor and trailer spring brakes. In a parked situation, the tractor and trailer brake valves will be in the ‘out’ position, which corresponds with the tractor and trailer spring brakes being applied.
Still in the parked position, the operator may push ‘in’ the yardvalve for the trailer in order to release the trailer brakes. Subsequently, the operator gets into the cab and accidentally pushes ‘in’, only the tractor brake valve. The tractor and trailer unit can then be driven away as all of the spring brakes are off as per normal. However, the trailer brake valve is in the ‘out’ position and, as a consequence, there will be no air pressure in the trailer brake supply line. Furthermore, the tractor protection system will work correctly and, thus, the trailer will receive no service brake pressure and, effectively, the trailer will have no brakes.
A possible outcome of such a situation is that the operator may feel a lack of brake efficiency and will push ‘in’ the trailer brake valve so that the system is restored to normal. Less likely, but nevertheless very possible, is that the operator needs maximum brake balance upon first application of the brakes, and in the absence of such balance, loses control of the tractor/trailer unit. This loss of control can result in a crash situation.
In a serious crash, the problem which led to the crash may be difficult to detect due to no actual defects being detectable, especially as all of the valves return to the ‘out’ position upon loss of air pressure. The chances of misdiagnosis and, therefore, a reoccurrence of accidents for the same reason is very high.